Cooper Union on Sept. 13 unveiled a model for its new nine-story academic building. Designed by Thom Mayne of Morphosis, the $120 building will rise on the east side of Third Ave. between Sixth and Seventh Sts. Construction is to start in 2006 and take about 20 months. The 200,000-sq.-ft. building will include a full-height atrium and 4,500 sq. ft. of retail space at street level. It will be the home of the Albert Nerken School of Engineering and will provide space for the School of Humanities and Social Science, the School of Art and Design and the Irwin S. Chanin School of Architecture. An exhibition including the model will be on view from Sept. 15 through Oct. 23 in Cooper Union’s Arthur S. Houghton Gallery in the school’s Foundation Building at Seventh St. and Third Ave.